domain model refinements and more iteration 3 prep. · domain model refinements and more iteration...
TRANSCRIPT
Domain Model Refinements
and more Iteration 3 Prep. CSSE 574: Session 6, Part 2
Steve Chenoweth
Phone: Office (812) 877-8974
Cell (937) 657-3885 Email:
Recall: Techniques for identifying
conceptual classes
Conceptual category lists
Noun phrase identification
Existing domain models
Conceptual Category List on NextGen
POS, Iteration 3
Category Examples
physical or tangible objects CreditCard, Check
transactions
CashPayment,
CreditPayment,
CheckPayment
other systems external to
ours
CreditAuthorizationService,
CheckAuthorizationService
organizations CreditAuthorizationService,
CheckAuthorizationService
records of finance, work,
contracts, legal matters AccountsReceivable
Noun Phrase Identification on NextGen
POS, iteration 3
Credit Account
Information
Payment
Authorization
Request
Payment
Authorization
Service Payment
Approval
Generalization-Specialization
Class Hierarchy
Conceptual classes, not
software classes
Domain modeling!
Generalization: finding
commonalities among
concepts
Superclass: general
concept
Subclass: specialized
concept
Why? Can understand concepts
in more general terms.
Payment gives our brains less
to deal with.
Generalization
Common features
of Payments
Genaralizations and Sets
All members of a conceptual
subclass set are members of their
superclass set – but may not
―partition‖ the set…
Is-a rule: Subclass is a superclass,
e.g., CashPayment is a Payment
Subclass Conformance—The 100% Rule
The subclass must conform to all of the
superclass’s attributes and associations.
As in, follow the Liskov Substitution
Principle!
"If for each object o1 of type S there is an
object o2 of type T such that for all
programs P defined in terms of T, the
behaviour of P is unchanged when o1 is
substituted for o2 then S is a subtype of T."
9
Quoted from http://www.blackwasp.co.uk/LSP.aspx.
Image of Barbara Liskov from
http://web.mit.edu/newsoffice/2009/turing-liskov-0310.html.
When should we define
a Conceptual Subclass?
Does this make sense…
for NextGen POS?
for other domains?
When should we define
a Conceptual Subclass? (continued)
When the subclass…
has additional attributes
has additional
associations
is operated on or
handled differently
represents an animated
thing that behaves
differently
Which of these
apply here?
Q3
When should we group classes and
extract a superclass?
Create a superclass when:
1. Potential subclasses represent variations of a
similar concept
(e.g., Video, Game → RentableItem)
2. Subclasses will conform to 100% and is-a rules
3. There are common attributes or associations
that could be pulled into superclass
Another Example
Abstract Conceptual Classes
If every member of a class C must be a
member of a subclass, then C is an abstract
conceptual class
What does this mean in
terms of our set idea?
Italics (or {abstract} keyword)
indicate abstract class
Be an Ontologist – go nuts on this!
15
Ontology = Basic categories of being
and their relations. Like these…